1. Field of the Invention
The present invention relates generally to transistors and switching circuits. More particularly, the present invention relates to III-nitride transistors and switching circuits.
2. Background Art
Silicon based transistors such as silicon metal-oxide-semiconductor field-effect transistors or MOSFETs may include the advantageous property of a body diode or an “intrinsic diode” due to their inherent silicon PN junctions. This “intrinsic diode” provides advantages such as inherent over-voltage (or under-voltage) protection for power conversion circuits without requiring a separate diode; thus reducing costs, improving efficiency, and simplifying circuit design.
On the other hand, III-nitride transistors such as gallium nitride high electron mobility transistors or GaN HEMTs are often preferable over traditional silicon based transistors for switching, and especially high voltage switching, applications. By providing higher breakdown voltage, higher temperature operation, reduced specific on-resistance, and other desirable traits, III-nitride transistors are especially suited for high power and high frequency switching applications such as efficient DC-DC power conversion circuits.
Unfortunately, since the “intrinsic diode” is only the result of a silicon FET structure, III-nitride transistors require a separate diode to provide the same benefits as the “intrinsic diode” in silicon transistors. However, integrating a monolithic diode in a GaN HEMT process is difficult and complex. Moreover, for high performance switching applications, the need for Schottky-like diode performance with low forward voltage drop and zero reverse recovery characteristics further complicates monolithic integration into a single device. Thus, while high performance III-nitride switching transistors are readily available, adoption is not yet as widespread in power conversion applications due to the lack of suitable methods to integrate a high performance diode with Schottky-like characteristics.
Thus, a solution is needed to provide III-nitride transistors such as GaN HEMTs with high performance Schottky-like diode functionality that is practical and not prohibitively complex or costly.